Carrington rotations
Convert a date to its Carrington rotation number and back, and browse rotation start and end times.
CR 3954
| Start | January 21, 2149 at 12:20 AM UTC |
|---|---|
| End | February 17, 2149 at 08:32 AM UTC |
| Length (days) | 27.34 |
Neighbouring rotations
| CR | Start | End | Length (days) |
|---|---|---|---|
| 3949 | September 6, 2148 at 11:45 AM UTC | October 3, 2148 at 06:14 PM UTC | 27.27 |
| 3950 | October 3, 2148 at 06:14 PM UTC | October 31, 2148 at 01:12 AM UTC | 27.29 |
| 3951 | October 31, 2148 at 01:12 AM UTC | November 27, 2148 at 08:33 AM UTC | 27.31 |
| 3952 | November 27, 2148 at 08:33 AM UTC | December 24, 2148 at 04:17 PM UTC | 27.32 |
| 3953 | December 24, 2148 at 04:17 PM UTC | January 21, 2149 at 12:20 AM UTC | 27.34 |
| 3954 | January 21, 2149 at 12:20 AM UTC | February 17, 2149 at 08:32 AM UTC | 27.34 |
| 3955 | February 17, 2149 at 08:32 AM UTC | March 16, 2149 at 04:24 PM UTC | 27.33 |
| 3956 | March 16, 2149 at 04:24 PM UTC | April 12, 2149 at 11:29 PM UTC | 27.29 |
| 3957 | April 12, 2149 at 11:29 PM UTC | May 10, 2149 at 05:30 AM UTC | 27.25 |
| 3958 | May 10, 2149 at 05:30 AM UTC | June 6, 2149 at 10:37 AM UTC | 27.21 |
| 3959 | June 6, 2149 at 10:37 AM UTC | July 3, 2149 at 03:21 PM UTC | 27.20 |
About this tool
A Carrington rotation is the time the Sun takes to turn once on its axis as seen from the Earth: 27.2753 days on average. The count was defined by the English astronomer Richard Carrington, who studied sunspots in the 1850s; rotation 1 began on 9 November 1853, and the numbering has run without interruption since.
Explorer computes the start of each rotation with the formula given by Jean Meeus in Astronomical Algorithms (chapter 29), implemented in its own astronomy library and checked against published dates. A rotation begins when the Carrington longitude L₀ of the central meridian passes through 0°; because the Earth moves along its orbit, the synodic period varies slightly around the mean, hence lengths of 27.2 to 27.3 days.
Observers use the rotation number as a calendar for the Sun: an active region that crosses the disc reappears about one rotation later, and the community activity heatmap shows one row per rotation so that returning regions line up. Enter a date to find its rotation, or a number to get the UTC start and end dates and the neighbouring rotations.